PCPP1 Practice Test 7 — 10 Questions

Question 1

You are processing a CSV file using csv.DictReader. If your input file lacks a header row, how do you provide the field names?

Accepted Answer

csv.DictReader(f, fieldnames=['a', 'b']). You pass the 'fieldnames' argument to the constructor to define the headers explicitly.

Answer

csv.DictReader(f, headers=['a', 'b'])

Answer

csv.DictReader(f).map(['a', 'b'])

Answer

csv.DictReader(f, columns=['a', 'b'])

Question 2

You are developing a Tkinter application that includes a Canvas widget for drawing a dynamic bar chart. The chart data updates every second, and you must redraw the bars. To avoid visual flicker and improve performance, you decide to reuse existing canvas items instead of deleting and recreating them. Which Canvas method should you use to change the height of an existing rectangle item identified by its item ID?

Accepted Answer

canvas.coords(item_id, x1, y1, x2, y2). To dynamically update the size of an existing canvas item, you should modify its coordinates. The coords() method allows you to set new coordinates for an item, effectively resizing or repositioning it without deleting and recreating. This is efficient and avoids flicker. Other methods like itemconfig() are for changing options like fill, move() only translates, and scale() applies proportional scaling, which is not ideal for precise height adjustments.

Answer

canvas.move(item_id, 0, delta_y)

Answer

canvas.scale(item_id, x_origin, y_origin, x_scale, y_scale)

Answer

canvas.itemconfig(item_id, height=new_height)

Question 3

Which magic method is triggered when an object is deleted using the 'del' keyword?

Accepted Answer

__del__. The __del__ method is called when the object's reference count reaches zero.

Answer

__clear__

Answer

__remove__

Answer

__destroy__

Question 4

Which method is used to customize the behavior of the 'in' operator?

Accepted Answer

__contains__. The __contains__ method is called when using the 'in' or 'not in' operators.

Answer

__has__

Answer

__find__

Answer

__in__

Question 5

When using the __call__ method to implement a decorator, what does the decorator receive as an argument?

Accepted Answer

The function to be decorated.. The decorator receives the function object that is being decorated as the argument to the constructor (if the decorator is a class instance) or directly if it is a function.

Answer

The arguments to the function.

Answer

The instance of the class.

Answer

The class object.

Question 6

How do you correctly call a method from a sibling class in a diamond inheritance structure using super()?

Accepted Answer

Use super() in each class to delegate to the next class in the MRO.. super() follows the Method Resolution Order (MRO), which correctly handles diamond inheritance by delegating calls to the next class in the chain, not just the parent.

Answer

Call the grandparent class directly.

Answer

Use the __bases__ attribute to iterate through parents.

Answer

Explicitly call the sibling class method by name.

Question 7

Which magic method is responsible for providing the informal string representation of an object, typically used for user-facing output?

Accepted Answer

__str__. The __str__ method is used for informal, readable string representations, whereas __repr__ is for formal, unambiguous representations.

Answer

__format__

Answer

__unicode__

Answer

__repr__

Question 8

Why does the 'abc' module provide the 'ABCMeta' metaclass?

Accepted Answer

To enforce abstract method implementation at instantiation.. ABCMeta is the metaclass that implements the logic to prevent instantiation of classes with abstract methods.

Answer

To allow private methods.

Answer

To improve method resolution speed.

Answer

To support multiple inheritance.

Question 9

Which magic method enables index access (e.g., obj[i])?

Accepted Answer

__getitem__. The __getitem__ method allows an object to support indexing.

Answer

__index__

Answer

__setitem__

Answer

__access__

Question 10

When naming a constant in Python, which convention does PEP 8 recommend?

Accepted Answer

UPPER_CASE_WITH_UNDERSCORES.. Constants should be named using all capital letters with underscores to separate words.

Answer

PascalCase.

Answer

snake_case.

Answer

CamelCase.